Esters of o-substituted hydroxy carboxylic acids and preparations thereof

ABSTRACT

Esters of O-substituted hydroxy carboxylic acids are provided having Formula 1, or 2, or both Formulas 1 and 2: 
     
       
         
         
             
             
         
       
     
     wherein R and R 1  are independently selected from the group consisting of substituted and unsubstituted, branched- and straight-chain, saturated, unsaturated, and polyunsaturated C 1 -C 22  alkyl, substituted and unsubstituted C 3 -C 8  cycloalkyl, substituted and unsubstituted C 6 -C 20  carbocyclic aryl, and substituted and unsubstituted C 4 -C 20  heterocyclic; wherein the heteroatoms are selected from sulfur, nitrogen, and oxygen; and wherein n is 1-6. Process of producing esters of O-substituted hydroxy carboxylic acids are also provided.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is an original application claiming priority toprovisional application U.S. Ser. No. 61/368,850 filed Jul. 29, 2010,herein incorporated by reference to the extent it does not contradictthe statements herein.

FIELD OF THE INVENTION

The present invention pertains to the field of esters of O-substitutedhydroxy carboxylic acids. The invention also pertains to processes forproducing O-substituted hydroxy carboxylic acids.

SUMMARY OF FIGURES

FIG. 1 shows the extent of hydrolysis over time in Example 14.

BACKGROUND OF THE INVENTION

Retinol (Vitamin A) and its derivatives have a long history as activeingredients in cosmetic compositions to improve the overall appearanceof the skin. Retinol itself is unstable and is toxic upon excessive use.Long-chain retinyl esters are sometimes preferred because they are morestable and less irritating to the skin. These esters are expected to bereadily hydrolyzed in the skin to afford retinol for metabolism and thusefficacy. Depending on the fatty acids, the hydrolysis product mayintroduce additional benefits too. Besides fatty acids, otherstructures, with various biological properties, are also desired inretinyl conjugates in order to improve and/or broaden the biologicalbenefits. Thus, a mild and general method is needed to link retinol orother skin care ingredients with interesting structures.

The most commonly used chemical preparation of esters involves thereaction of an alcohol and an acid chloride or anhydride (activatedcarboxylate) in the presence of a base. Nucleophilic substitution of acarboxylate on an alkyl halide or sulfonate is another effective method,provided that the halide or sulfonate is readily available. In the caseof retinyl esters, both routes proved to be suboptimal since retinol andretinyl esters tend to be unstable under these types of reactionconditions.

There have been several reports of chemical and enzymatic syntheses ofretinyl esters. The preparation of a retinol-ascorbic acid conjugate hasbeen described in the literature where the two substructures areconnected by a glycolate linker using a two-step chemical route.Enzymatic esterification or trans-esterification preparation of retinylesters are usually catalyzed by native or modified enzymes. Thesereactions generally only afford incomplete conversion to the desiredretinyl ester product unless the by-product is removed from the reactionby the use of a large amount of molecular sieves, using reducedpressure, and/or by purging the reaction mixture with an inert gas. Thesubstrate specificity of many enzymes generally limits this type oftransformation to straight-chain carboxylic acids, especially fattyacids. Since the synthesis and hydrolysis of esters are catalyzed by thesame family of enzymes, i.e. lipases, esters that cannot beenzymatically prepared are less likely to be readily hydrolyzed byenzymes in the skin to release the active agent retinol. Although insome cases it is possible to esterify retinol by chemical methods withchallenging species, such as branched carboxylic acids or othersterically-hindered species, these esters might only offer marginalefficacy since they still need to be hydrolyzed in the skin to releaseretinol to be effective. Thus, a process for conjugating retinol orother skin care ingredients with a broad variety of species which wouldrelease retinol in vivo would be of interest.

A specially-designed linker, which is used to connect skin careingredients with a variety of species, can be envisioned to solve thischallenge. It would be highly desirable that this connection occur undermild conditions and in high yield. This would allow the preparation ofconjugates of skin care ingredients and other species that are difficultto directly connect. More importantly, this linker should alsofacilitate the enzymatic ester hydrolysis and thus the ready release ofthe free skin care ingredient in the skin.

SUMMARY OF THE INVENTION

In one embodiment of this invention, an ester of O-substituted hydroxycarboxylic acids is provided having Formula 1 or Formula 2,

wherein R and R¹ are independently selected from the group consisting ofsubstituted and unsubstituted, branched- and straight-chain, saturated,unsaturated, and polyunsaturated C₁-C₂₂ alkyl, substituted andunsubstituted C₃-C₈ cycloalkyl, substituted and unsubstituted C₆-C₂₀carbocyclic aryl, and substituted and unsubstituted C₄-C₂₀ heterocyclic;wherein the heteroatoms are selected from sulfur, nitrogen, and oxygen;and wherein n is 1-6.

In another embodiment of the invention, a process is provided to produceat least one ester of an O-substituted hydroxy carboxylic acid havingFormula 1, or 2:

wherein R and R¹ are independently selected from the group consisting ofsubstituted and unsubstituted, branched- and straight-chain, saturated,unsaturated, and polyunsaturated C₁-C₂₂ alkyl, substituted andunsubstituted C₃-C₈ cycloalkyl, substituted and unsubstituted C₆-C₂₀carbocyclic aryl, and substituted and unsubstituted C₄-C₂₀ heterocyclic;wherein the heteroatoms are selected from sulfur, nitrogen, and oxygen;and wherein n is 1-6, the process comprising:

a) contacting an alcohol having Formula 3

R—OH  3

with a terminal halogen-substituted straight-chain carboxylic acidhaving Formula 4

X(CH₂)_(n)COOH  4

or a short-chain ester having Formula 5

X(CH₂)_(n)COOR⁵  5

in the presence of an enzyme to produce an intermediate having theFormula 6,

wherein R is independently selected from the group consisting ofsubstituted and unsubstituted, branched- and straight-chain, saturated,unsaturated, and polyunsaturated C₂-C₂₂ alkyl, substituted andunsubstituted C₃-C₈ cycloalkyl, substituted and unsubstituted C₆-C₂₀carbocyclic aryl, and substituted and unsubstituted C₄-C₂₀ heterocyclic;wherein the heteroatoms are selected from sulfur, nitrogen, and oxygen;wherein R⁵ is a straight or branched C₁-C₄-alkyl or alkenyl, X is ahalogen atom, and n is 1-6;

b) reacting the intermediate with a carboxylic acid or alcoholoptionally in the presence of a base and optionally in the presence of acatalyst to produce at least one ester of Formula 1 or 2.

DETAILED DESCRIPTION

In one embodiment of this invention, novel compounds have beendiscovered represented by the general formulas 1 and 2:

wherein R and R¹ are independently selected from substituted andunsubstituted, branched- and straight-chain, saturated, unsaturated, andpolyunsaturated C₁-C₂₂ alkyl, substituted and unsubstituted C₃-C₈cycloalkyl, substituted and unsubstituted C₆-C₂₀ carbocyclic aryl, andsubstituted and unsubstituted C₄-C₂₀ heterocyclic wherein theheteroatoms are selected from sulfur, nitrogen, and oxygen and n is 1-6.

In another embodiment, R and R¹ are independently selected from thegroup consisting of substituted and unsubstituted, branched- andstraight-chain saturated C₁-C₂₂ alkyl, substituted and unsubstituted,branched- and straight-chain C₂-C₂₂ alkenyl, substituted andunsubstituted, branched- and straight-chain C₄-C₂₂ dienyl, substitutedand unsubstituted, branched- and straight-chain C₆-C₂₂ trienyl,substituted and unsubstituted, branched- and straight-chain C₈-C₂₂tetraenyl, substituted and unsubstituted, branched- and straight-chainC₁₀-C₂₂ pentaenyl, substituted and unsubstituted C₃-C₈ cycloalkyl,substituted and unsubstituted C₄-C₂₀ heterocyclic, or mixtures thereof,and n is 1-6.

The alkyl, alkenyl, dienyl, trienyl, tetraenyl, pentaenyl, andcycloalkyl groups which may be represented by R and R¹ may be straight-or branched-chain aliphatic hydrocarbon radicals containing up to about22 carbon atoms and may be substituted, for example, with one to fivegroups selected from C₁-C₆-alkoxy, carboxyl, amino, C₁-C₁₅aminocarbonyl, C₁-C₁₅ amido, cyano, C₂-C₆-alkoxycarbonyl,C₂-C₆-alkanoyloxy, hydroxy, aryl, heteroaryl, thiol, thioether, C₂-C₁₀dialkylamino, C₃-C₁₅ trialkylammonium and halogen. The terms“C₁-C₆-alkoxy”, “C₂-C₆-alkoxycarbonyl”, and “C₂-C₆-alkanoyloxy” are usedto denote radicals corresponding to the structures —OR², —CO₂R², and—OCOR², respectively, wherein R² is C₁-C₆-alkyl or substitutedC₁-C₆-alkyl. The terms “C₁-C₁₅ aminocarbonyl” and “C₁-C₁₅ amido” areused to denote radicals corresponding to the structures —NHCOR³,—CONHR³, respectively, wherein R³ is C₁-C₁₅-alkyl or substitutedC₁-C₁₅-alkyl. The term “C₃-C₈-cycloalkyl” is used to denote a saturated,carbocyclic hydrocarbon radical having three to eight carbon atoms. Thebranching and/or substitution of R and R¹ may connect to form a ring.

The aryl groups which R and R¹ may represent (or any aryl substituents)may include phenyl, naphthyl, or anthracenyl and phenyl, naphthyl, oranthracenyl substituted with one to five substituents selected fromC₁-C₆-alkyl, substituted C₁-C₆-alkyl, C₆-C₁₀ aryl, substituted C₆-C₁₀aryl, C₁-C₆-alkoxy, halogen, carboxy, cyano, C₁-C₆-alkanoyloxy,C₁-C₆-alkylthio, C₁-C₆-alkylsulfonyl, trifluoromethyl, hydroxy,C₂-C₆-alkoxycarbonyl, C₂-C₆-alkanoylamino and —OR⁴, —S—R⁴, —SO₂—R⁴,—NHSO₂R⁴ and —NHCO₂R⁴, wherein R⁴ is phenyl, naphthyl, or phenyl ornaphthyl substituted with one to three groups selected from C₁-C₆-alkyl,C₆-C₁₀ aryl, C₁-C₆-alkoxy and halogen.

The heterocyclic groups which R and R¹ may represent (or any heteroarylsubstituents) include 5- or 6-membered ring containing one to threeheteroatoms, excluding ascorbic acid. The heteroatoms are independentlyselected from the group consisting of oxygen, sulfur and nitrogen.Examples of such heterocyclic groups are pyranyl, oxopyranyl,dihydropyranyl, oxodihydropyranyl, tetrahydropyranyl, thienyl, furyl,pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl,isoxazolyl, triazolyl, thiadiazolyl, oxadiazolyl, tetrazolyl, pyridyl,pyrimidyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, indolyl and thelike. The heterocyclic radicals may be substituted, for example, with upto three groups such as C₁-C₆-alkyl, C₁-C₆-alkoxy, substitutedC₁-C₆-alkyl, halogen, C₁-C₆-alkylthio, aryl, arylthio, aryloxy,C₂-C₆-alkoxycarbonyl and C₂-C₆-alkanoylamino. The heterocyclic radicalsalso may be substituted with a fused ring system, e.g., a benzo ornaphtho residue, which may be unsubstituted or substituted, for example,with up to three of the groups set forth in the preceding sentence. Theterm “halogen” is used to include fluorine, chlorine, bromine, andiodine.

In another embodiment of the invention, R can be retinyl and R¹ can beany of the radicals previously described in this disclosure.

Examples of the compounds of the invention include those represented byFormula 1; wherein n is 1, R-0 is retinyl or oleyl and R¹CO arecarnitinoyl, shikimoyl, 4-methoxycinnamoyl, feruloyl, salicyloyl,nicotinoyl, retinoyl or 2-cyano-3,3-diphenylacryloyl, and formula 2wherein n is 1, R—O is retinyl and R¹ is2-hydroxymethyl-4H-pyran-4-on-5-yl.

The novel chemoenzymatic process of our invention involves 2 steps. Thefirst step comprises the enzymatic reaction of an alcohol 3:

R—OH  3

with a terminal halogen-substituted straight-chain carboxylic acidX(CH₂)_(n)COOH or short-chain ester X(CH₂)_(n)COOR⁵ in the presence ofan enzyme with or without methods for the removal of the water oralcohol by-product to form the desired intermediate 4, wherein R isdefined as above, R⁵ is a straight or branched C₁-C₄-alkyl or alkenyl, Xis a halogen atom and n is 1-6.

The first step of the process is carried out without solvent, or in aninert solvent chosen from cyclic or acyclic ether solvents, such as,diethyl ether, diisopropyl ether, tert-butyl methyl ether, ortetrahydrofuran; aromatic hydrocarbons, such as, benzene, toluene, orxylene; aliphatic or alicyclic saturated or unsaturated hydrocarbons,such as, hexane, heptane, cyclohexane, or limonene; halogenatedhydrocarbons, such as, dichloromethane, dichloroethane, dibromoethane,tetrachloroethylene, or chlorobenzene; polar aprotic solvents, such as,acetonitrile, dimethyl formamide, or dimethyl sulfoxide; or mixturesthereof. In one embodiment, no solvent is utilized in the first step. Inanother embodiment, at least one inert solvent is utilized selected fromthe group consisting of toluene, limonene, heptanes, and acetonitrile.The first step of the process may be carried out at a temperaturebetween about −100° C. to about 100° C. In another embodiment, the firststep of the process can be carried out at a temperature between about−100° C. to the boiling point of the inert solvent. Other temperatureranges are from about 0° C. to about 60° C. and from about 20° C. toabout 50° C. The amount of halogen-substituted acid or short-chain estermay be between about 0.85 and about 20 equivalents based on the weightof the compound of Formula 3. Other amounts of halogen-substituted acidor short-chain ester range from about 1 and about 10 equivalents andfrom about 1 to about 1.5 equivalents.

The enzyme used in the first step of the process is chosen from aprotease, a lipase, or an esterase. In one embodiment, the enzyme is alipase. These lipases may be in the form of whole cells, isolated nativeenzymes, or immobilized on supports. Examples of these lipases include,but are not limited to, Lipase PS (from Pseudomonas sp), Lipase PS-C(from Psuedomonas sp immobilized on ceramic), Lipase PS-D (fromPseudomonas sp immobilized on diatomaceous earth), Lipoprime 50T,Lipozyme TL IM, or Novozym 435 (Candida antarctica lipase B immobilizedon acrylic resin). The amount of enzyme can range from about 0.01 toabout 200 wt % based on the alcohol of Formula 3. The amount of enzymecan also range from about 0.1 to about 50 wt % based on the alcohol ofFormula 3.

In the first step of the process, removal of the water or alcoholbyproducts can be done chemically via a water or alcohol absorbent(e.g., molecular sieves) or by physical removal of the water or alcohol.This by-product removal can be conducted by evaporation, either bypurging the reaction mixture with an inert gas such as nitrogen, argon,or helium, or by performing the reaction at reduced pressures, or both,as these conditions can afford >98% conversion of retinol toIntermediate 4. The pressure for the reaction can be between 1 torr andambient pressure or between 50 torr and ambient pressure. Any inertsolvent that is included in the first step of this process may or maynot be removed along with the water or alcohol. Examples of Formula 3R—OH include, but are not limited to, retinol and oleyl alcohol.

The second step to generate the ester of o-substituted hydroxylcarboxylic acid Formula 1 comprises the reaction of Intermediate 4 withthe desired carboxylic acid or alcohol optionally in the presence of abase. The second step of the process is carried out without solvent orin an inert solvent chosen from water, cyclic or acyclic ether solvents,such as, but not limited to, diethyl ether, diisopropyl ether,tert-butyl methyl ether, or tetrahydrofuran; aromatic hydrocarbons, suchas, benzene, toluene, or xylene; aliphatic or alicyclic saturated orunsaturated hydrocarbons, such as, hexane, heptane, cyclohexane, orlimonene; halogenated hydrocarbons, such as, dichloromethane,dichloroethane, dibromoethane, tetrachloroethylene, or chlorobenzene;ester solvents, such as methyl acetate, ethyl acetate, methylpropionate, or isopropyl acetate; polar aprotic solvents, such as,acetonitrile, dimethyl formamide, or dimethyl sulfoxide, or mixturesthereof. In another embodiment of the invention, no solvent is utilized.In another embodiment, at least one inert solvent is utilized selectedfrom the group consisting of tetrahydrofuran, dimethyl formamide,dimethyl sulfoxide, acetone, acetonitrile, ethyl acetate, toluene,water, and mixtures thereof.

The second step of the process may be carried out at a temperaturebetween about −100° C. and about 100° C. In another embodiment, thesecond step of the process can be carried out at a temperature betweenabout −100° C. and the boiling point of the inert solvent. Othertemperature ranges are from about 0° C. to about 60° C. and from about20° C. to about 50° C. The amount of the acid or alcohol may be betweenabout 0.85 and about 20 equivalents based on Intermediate 4. Otherranges are from about 1 to about 10 equivalents or from about 1 to about1.5 equivalents.

If included, the base is chosen from tertiary amines, metal hydroxides,metal alkoxides, metal carbonates, or metal bicarbonates. In oneembodiment, at least one base is selected from the group consisting oftriethylamine, N,N-diisopropylethylamine, sodium hydroxide, potassiumhydroxide, sodium carbonate, potassium carbonate, and potassiumbicarbonate. The amount of base can be from about 0.4 molar equivalentsto about 20 molar equivalents based on the ester of Formula 4. Inanother embodiment, the amount is between about 0.5 and about 10equivalents or between about 0.5 and about 1.5 equivalents.

The second step of the process may also include the presence of acatalyst chosen from quaternary ammonium salts, quaternary phosphoniumsalts, or crown ethers. Examples of such catalysts include, but are notlimited to, tetrabutylammonium bromide, tetraheptylammonium bromide,tetraheptylammonium chloride, methyl tribuylammonium chloride, methyltricaprylammonium chloride, tetrabutylphosphonium chloride, and12-crown-6. The amount of catalyst may be between about 0.005 and about1.0 molar equivalents based on the ester of Formula 4. Another range isfrom about 0.01 to about 0.5 equivalents.

The intermediate of Formula 3 and the esters of O-substituted hydroxycarboxylic acids of Formulas 1 and 2 of the process may be isolatedusing methods known to those of skill in the art, e.g., extraction,filtration, or crystallization.

The esters of O-substituted hydroxy carboxylic acids can be utilized incompositions, such as cosmetic compositions, skin care compositions andthe like. The compositions can be useful, for example, for reducing skinroughness, fine lines, and wrinkles, improving photo-damaged skin,regenerating skin, reducing skin hyper-pigmentation, and reducingirritation and/or inflammatory reaction in skin.

Typical cosmetic and/or skin care compositions of the invention containat least 0.001% by weight of the O-substituted hydroxy carboxylic acidsaccording to the present invention. For example, the compositions cancontain from about 0.001% to about 20.0% by weight or from about 0.01 toabout 10.0% by weight of the O-substituted hydroxy carboxylic acidsaccording to the present invention. Lower concentrations may be employedfor less pronounced conditions, and higher concentrations may beemployed with more acute conditions. Suggested ranges also depend uponany adjunct ingredients employed in the compositions.

The cosmetic and skin care compositions of the invention may alsocontain other skin conditioning ingredients in addition to O-substitutedhydroxy carboxylic acids. Such compositions may also contain other skiningredients such as retinol, retinyl esters, tetronic acid, tetronicacid derivatives, hydroquinone, kojic acid, gallic acid, arbutin,α-hydroxyl acids, and fatty acid esters of ascorbic acid. Such otheringredients are known to those of skill in the art.

Typically, topical application to skin sites is accomplished inassociation with a carrier. Where employed, the carrier is inert in thesense of not bringing about a deactivation or oxidation of active oradjunct ingredient(s), and in the sense of not bringing about anyadverse effect on the skin areas to which it is applied. For example,the compounds according to the present invention are applied inadmixture with a dermatologically acceptable carrier or vehicle (e.g.,as a lotion, cream, ointment, soap, stick, or the like) so as tofacilitate topical application and, in some cases, provide additionalbeneficial effects as might be brought about, e.g., by moisturizing ofthe affected skin areas. Many preparations are known in the art, andinclude lotions containing oils and/or alcohols and emollients such asolive oil, hydrocarbon oils and waxes, silicone oils, other vegetable,animal or marine fats or oils, glyceride derivatives, fatty acids orfatty acid esters or alcohols or alcohol ethers, lecithin, lanolin andderivatives, polyhydric alcohols or esters, wax esters, sterols,phospholipids and the like, and generally also emulsifiers (nonionic,cationic or anionic). These same general ingredients can be formulatedinto a cream rather than a lotion, or into gels, or into solid sticks byutilization of different proportions of the ingredients and/or byinclusion of thickening agents such as gums or other forms ofhydrophilic colloids.

The novel processes provide by the present invention are furtherillustrated by the following examples.

Example 1 Preparation of Retinyl Bromoacetate

To an amber round bottle, retinol in toluene (59.7 wt % retinol; 30.65g; 18.30 g retinol; 63.9 mmol) was added followed by methyl bromoacetate(10.75 g; 70.2 mmol; 1.1 equiv.) and Novozym 435 (0.46 g). The mixturewas stirred at room temperature and purged with a stream of nitrogenthrough the mixture for 26 hours to afford 96.7% conversion of retinolto intermediate 4 according to HPLC analysis. The mixture was filtered,and the solid was washed with heptanes. The filtrate was concentrated togive the desired product as a viscous yellow oil (25.32 g, 97%).Intermediate 4 was used in the subsequent reactions without furtherpurification.

HPLC (High Performance Liquid Chromatography) (4.6×150 mm Zorbax SB-C8column [Agilent], 3.5μ thickness, 95:5 methanol:water (containing 0.1%trifluoroacetic acid) for 10 min, detection at 325 nm): t_(R) 3.7 min(retinol); t_(R) 4.9 min (retinyl bromoacetate).

Example 2 Preparation of Retinyl O-Carnitinoylglycolate Bromide

Carnitine inner salt (0.65 g, 4 mmol) was suspended in dimethylformamide(3 mL). Retinyl bromoacetate (1.628 g; 4 mmol) in dimethyl formamide (2mL) was added dropwise. The mixture was stirred at room temperature for5 hours to afford >99% conversion of retinyl bromoacetate to the esteraccording to HPLC analysis. The mixture was filtered and concentrated invacuo to give 2.2 g of a yellow, very hygroscopic solid. ¹H NMR(Hydrogen-1-Nuclear Magnetic Resonance) (CDCl₃) δ (ppm): 6.67 (dd, 1H,J=15.0, 11.4 Hz), 6.27 (d, 1H, J=15.0 Hz), 6.3-6.0 (m, 3H), 5.57 (t, 1H,J=7.2 Hz), 4.9-4.7 (m, 2H), 4.68 (d, 2H, J=2.4 Hz), 3.9-3.7 (m, 2H),3.45 (br s, 9H), 3.0-2.8 (m, 4H), 2.02 (t, 2H, J=6.6 Hz), 1.96 (s, 3H),1.89 (s, 3H), 1.71 (s, 3H), 1.65-1.55 (m, 2H), 1.5-1.4 (m, 2H), 1.02 (s,6H).

HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5μ thickness, 95:5methanol:water (containing 0.1% trifluoroacetic acid) for 10 min,detection at 325 nm): t_(R) 2.0 min (retinyl O-carnitinoylglycolatebromide); t_(R) 5.1 min (retinyl bromoacetate).

Example 3 Preparation of Retinyl O-Feruloylglycolate

Ferulic acid (2.913 g; 15 mmol) was mixed with potassium carbonate(1.036 g; 7.5 mmol) in dimethyl formamide (30 mL). The mixture wasstirred for 45 min, then retinyl bromoacetate (6.112 g; 15 mmol) wasadded dropwise. The mixture was stirred overnight to afford >99%conversion of retinyl bromoacetate to the ester according to HPLCanalysis. The mixture was then diluted with toluene (300 mL) and washedwith water and brine repeatedly. The organic phase was dried andconcentrated in vacuo to give the desired product as a yellow solid(7.95 g; 93%). ¹H NMR (CDCl₃) δ (ppm): 7.70 (d, 1H, J=15.9 Hz), 7.09(dd, 1H, J=8.1, 1.8 Hz), 7.04 (d, 1H, J=1.8 Hz), 6.92 (d, 1H, J=8.1 Hz),6.67 (dd, 1H, J=15.0, 11.4 Hz), 6.38 (d, 1H, J=16.2 Hz), 6.27 (d, 1H,J=15.3 Hz), 6.3-6.0 (m, 3H), 5.61 (t, 1H, J=7.2 Hz), 4.85 (d, 2H, J=7.2Hz), 4.75 (s, 2H), 3.92 (s, 3H), 2.02 (t, 2H, J=6.3 Hz), 1.96 (s, 3H),1.90 (s, 3H), 1.71 (s, 3H), 1.65-1.55 (m, 2H), 1.5-1.4 (m, 2H), 1.02 (s,6H).

HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5μ thickness, 95:5methanol:water (containing 0.1% trifluoroacetic acid) for 10 min,detection at 325 nm): t_(R) 4.3 min (retinyl O-feruloylglycolate); t_(R)4.8 min (retinyl bromoacetate).

Example 4 Preparation of Retinyl O-Shikimoylglycolate

Shikimic acid (2.606 g; 15 mmol) was mixed with potassium carbonate(1.046 g; 7.5 mmol) in dimethyl sulfoxide (20 mL). The mixture wasstirred for 45 min and then placed in a cold bath. At 12° C., retinylbromoacetate (6.023 g; 14.5 mmol) in dimethyl sulfoxide (10 mL) wasadded dropwise. The mixture was stirred for 2 hours to afford 98%conversion of retinyl bromoacetate to the ester according to HPLCanalysis. The mixture was then diluted with ethyl acetate (150 mL) andwashed with water and brine repeatedly. The organic phase was dried andconcentrated in vacuo to give the desired product as a yellow solid(6.573 g; 91%). ¹H NMR (CDCl₃) δ (ppm): 6.96 (br s, 1H), 6.65 (dd, 1H,J=15.0, 11.4 Hz), 6.26 (d, 1H, J=15.0 Hz), 6.2-6.0 (m, 3H), 5.58 (t, 1H,J=7.2 Hz), 4.81 (d, 2H, J=7.5 Hz), 4.69 (s, 2H), 4.5-4.4 (m, 1H),4.05-3.95 (m, 1H), 3.7-3.6 (m, 1H), 2.95-2.95 (m, 1H), 2.3-2.2 (m, 1H),2.01 (t, 2H, J=6.0 Hz), 1.95 (s, 3H), 1.88 (s, 3H), 1.71 (s, 3H),1.65-1.55 (m, 2H), 1.5-1.4 (m, 2H), 1.02 (s, 6H).

HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5μ thickness, 95:5methanol:water (containing 0.1% trifluoroacetic acid) for 10 min,detection at 325 nm): t_(R) 3.0 min (retinyl O-shikimoylglycolate);t_(R) 4.7 min (retinyl bromoacetate).

Example 5 Preparation of Retinyl O-(4-Methoxycinnamoyl)glycolate

4-Methoxycinnamic acid (4.296 g; 24 mmol) was mixed with potassiumcarbonate (1.665 g; 12 mmol) in dimethyl formamide (15 mL). The mixturewas stirred for 5 min and placed in a cold bath. At −8° C., retinylbromoacetate (10.805 g; 26.5 mmol) in dimethyl formamide (15 mL) wasadded dropwise. The mixture was stirred overnight at room temperature.The mixture was then diluted with ethyl acetate (200 mL) and washed withwater, 10% K₂CO₃ and brine repeatedly. The organic phase was dried andconcentrated in vacuo to give the desired product as a yellow viscousoil (10.321 g; 85%). ¹H NMR (CDCl₃) δ (ppm): 7.74 (d, 1H, J=15.6 Hz),7.50 (d, 2H, J=9.3 Hz), 6.91 (d, 2H, J=9.0 Hz), 6.66 (dd, 1H, J=15.0,11.4 Hz), 6.40 (d, 1H, J=15.6 Hz), 6.28 (d, 1H, J=15.0 Hz), 6.2-6.0 (m,3H), 5.62 (t, 1H, J=7.8 Hz), 4.85 (d, 2H, J=6.9 Hz), 4.74 (s, 2H), 3.84(s, 3H), 2.02 (t, 2H, J=6.0 Hz), 1.96 (s, 3H), 1.90 (s, 3H), 1.71 (s,3H), 1.65-1.55 (m, 2H), 1.5-1.4 (m, 2H), 1.02 (s, 6H).

HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5μ thickness, 95:5methanol:water (containing 0.1% trifluoroacetic acid) for 10 min,detection at 325 nm): t_(R) 3.0 min (retinylO-(4-methoxycinnamoyl)glycolate); t_(R) 4.7 min (retinyl bromoacetate).

Example 6 Preparation of RetinylO-(2-Hydroxymethyl-4H-pyran-4-on-5-yl)glycolate

Kojic acid (142 mg; 1.0 mmol) was mixed with potassium carbonate (69 mg;0.50 mmol) in dimethyl formamide (5 mL). Retinyl bromoacetate (421 mg;1.03 mmol) was added dropwise. The mixture was stirred for 5 hours. Themixture was then diluted with ethyl acetate and washed with water twice.The organic phase was dried and concentrated in vacuo to give thedesired product as a yellow viscous oil (548 mg). ¹H NMR (CDCl₃) δ(ppm): 8.02 (s, 1H), 6.67 (dd, 1H, J=15.0, 11.4 Hz), 6.55 (s, 1H), 6.28(d, 1H, J=15.0 Hz), 6.2-6.0 (m, 3H), 5.61 (t, 1H, J=7.8 Hz), 4.85 (d,2H, J=5.4 Hz), 4.73 (s, 2H), 4.49 (s, 2H), 2.02 (t, 2H, J=6.0 Hz), 1.98(s, 3H), 1.91 (s, 3H), 1.73 (s, 3H), 1.65-1.55 (m, 2H), 1.5-1.4 (m, 2H),1.04 (s, 6H).

HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5μ thickness, 95:5methanol:water (containing 0.1% trifluoroacetic acid) for 10 min,detection at 325 nm): t_(R) 3.4 min (retinylO-(2-hydroxymethyl-4H-pyran-4-on-5-yl)glycolate); t_(R) 5.4 min (retinylbromoacetate).

Example 7 Preparation of Retinyl O-Salicyloylglycolate

Salicylic acid (4.576 g; 33.1 mmol) was mixed with potassium carbonate(2.093 g; 15.1 mmol) in dimethyl formamide (18 mL). The mixture wasstirred for 5 min and then placed in an ice bath. At 0° C., retinylbromoacetate (12.221 g; 30.0 mmol) in dimethyl formamide (12 mL) wasadded dropwise. The mixture was stirred overnight at room temperature.More salicylic acid (414 mg, 3.0 mmol) and more potassium carbonate (414mg, 3.0 mmol) were added. The mixture was stirred for another 7 hours atroom temperature. The mixture was then diluted with diethyl ether (150mL) then washed with water (15 mL×2), 10% potassium bicarbonate (15 mL)and brine (15 mL). The organic phase was dried and concentrated in vacuoto give the desired product as a yellow solid (13.351 g; 96%). ¹H NMR(CDCl₃) δ (ppm): 7.93 (dd, 1H, J=8.1, 1.8 Hz), 7.55-7.45 (m, 1H),7.02-6.98 (m, 1H), 6.94-6.87 (m, 1H), 6.67 (dd, 1H, J=15.0, 11.4 Hz),6.27 (d, 1H, J=15.0 Hz), 6.2-6.0 (m, 3H), 5.61 (t, 1H, J=7.5 Hz), 4.87(d, 2H, J=7.2 Hz), 4.87 (s, 2H), 2.02 (t, 2H, J=6.0 Hz), 1.96 (s, 3H),1.90 (s, 3H), 1.71 (s, 3H), 1.65-1.55 (m, 2H), 1.5-1.4 (m, 2H), 1.02 (s,6H).

HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5μ thickness, 95:5methanol:water (containing 0.1% trifluoroacetic acid) for 10 min,detection at 325 nm): t_(R) 6.6 min (retinyl O-salicyloylglycolate);t_(R) 5.3 min (retinyl bromoacetate).

Example 8 Preparation of Retinyl O-Salicyloylglycolate (EX001013-161)

Salicylic acid (33.1 g; 0.24 mol; 1.2 equiv) was combined with 190 mL ofnitrogen-purged ethyl acetate in a 1-L reactor at 20° C. Triethylamine(41.8 mL; 0.30 mol; 1.5 equiv) was added to afford a homogeneoussolution with an attendant exotherm to 38° C. The mixture was cooled to20° C., and retinyl bromoacetate (81.4 g; 200 mmol) dissolved in 75 mLof purged ethyl acetate was added over 15 min with a slight exotherm (to21.4° C.) and then washed in with 15 mL of ethyl acetate. The mixturewas stirred for 19 h at room temperature during which a significantamount of precipitate was formed and HPLC analysis indicated >99.5%conversion to product. The mixture was washed with water (280 mL) andthen diluted with 280 mL of ethyl acetate. The organic solution waswashed with 1:1 methanol:1.5M HCl, then with 5% aqueous sodiumbicarbonate (250 mL). The organic phase was dried with magnesium sulfateand concentrated in vacuo to give the desired product as a thick yellowoil (82.47 g; 89% yield).

Example 9 Preparation of Retinyl O-Nicotinoylglycolate

Nicotinic acid (5.171 g; 42.0 mmol) was mixed withN,N-diisopropylethylamine (7.0 mL; 40.2 mmol) in dimethyl formamide (60mL). The mixture was stirred for 5 min and then placed in a cold bath.At −8° C., retinyl bromoacetate (14.555 g; 35.7 mmol) in dimethylformamide (15 mL) was added dropwise. The yellow solution was stirredovernight at room temperature. The resulting orange solution was thenpoured into 150 mL diethyl ether and washed in with 50 mL diethyl ether.After being washed with water (20 mL×3) and 5% sodium bicarbonate (20mL), the organic phase was dried and concentrated in vacuo to give thedesired product as a pale orange yellow solid (13.4 g; 85%). ¹H NMR(CDCl₃) δ (ppm): 9.29 (d, 1H, d=0.9 Hz), 8.84-8.79 (m, 1H), 8.4-8.3 (m,1H), 7.47-7.39 (m, 1H), 6.67 (dd, 1H, J=15.0, 11.4 Hz), 6.27 (d, 1H,J=15.0 Hz), 6.2-6.0 (m, 3H), 5.61 (t, 1H, J=7.5 Hz), 4.90 (s, 2H), 4.87(d, 2H, J=7.8 Hz), 2.02 (t, 2H, J=6.0 Hz), 1.96 (s, 3H), 1.90 (s, 3H),1.71 (s, 3H), 1.65-1.55 (m, 2H), 1.5-1.4 (m, 2H), 1.02 (s, 6H).

HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5μ thickness, 95:5methanol:water (containing 0.1% trifluoroacetic acid) for 10 min,detection at 325 nm): t_(R) 5.6 min (retinyl O-nicotinoylglycolate);t_(R) 5.3 min (retinyl bromoacetate).

Example 10 Synthesis of RetinylO-(2-Cyano-3,3-diphenyl-acryloyl)glycolate

2-Cyano-3,3-diphenyl acrylic acid (1.2 g, 4.8 mmol, 1.3 eq), 45 wt %potassium hydroxide (0.38 mL, 4.4 mmol, 1.2 eq) and 8 mL water wereadded to a 50 mL, 3-neck flask equipped with a stir bar, nitrogenbubbler and rubber septum. The mixture was stirred under a flow ofnitrogen until a homogeneous solution was obtained (about 10 minutes).Tetraheptylammonium bromide (0.18 g, 0.37 mmol, 0.1 eq) was added andthe mixture was stirred for 15 minutes. Retinyl bromoacetate (1.5 g, 3.7mmol, 1.0 eq) was added in 5 mL of toluene. After 15 minutes the mixturebecame very thick, but continued to stir well. It was left to stir overnight at room temperature, at which point HPLC analysis indicated noretinyl bromoacetate. The mixture was transferred to a separatory funnelusing toluene and the bottom water layer removed. The organic layer waswashed with 15 mL water, then 15 mL of a saturated sodium bicarbonatesolution and dried over sodium sulfate. It was concentrated in vacuo toafford 2.52 g of an orange-colored solid. ¹H NMR (toluene-d₈) δ (ppm):7.25-6.99 (m, 10H), 6.68 (dd, 1H, J=15.0, 11.4 Hz), 6.35-6.12 (m, 4H),5.52 (t, 1H, J=7.2 Hz), 4.62 (d, 2H, J=7.2 Hz), 4.25 (s, 2H), 2.02 (t,2H, J=6.0 Hz), 1.92 (s, 3H), 1.82 (s, 3H), 1.70 (s, 3H), 1.68-1.60 (m,2H), 1.56-1.48 (m, 2H), 1.16 (s, 6H).

HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5μ thickness, 95:5methanol:water (containing 0.1% trifluoroacetic acid) for 10 min,detection at 325 nm): t_(R) 6.070 min (retinyl bromoacetate); t_(R)6.488 min (retinyl O-(2-cyano-3,3-diphenyl-acryloyl)glycolate).

Example 11 Preparation of Oleyl Bromoacetate

Technical grade oleyl alcohol (85 wt %; 10 g; 37.2 mmol) was combinedwith Novozym 435 (200 mg) in an amber bottle. Methyl bromoacetate (6.84g; 44.7 mmol; 1.2 equiv.) was added, and the mixture was sealed andstirred at room temperature overnight to afford about 50% conversion tooleyl bromoacetate. The mixture was then purged with a subsurface streamof nitrogen 2.5 days to afford 98.5% conversion of oleyl alcohol tooleyl bromoacetate according to GC analysis. The mixture was filtered,and the solid was washed with toluene. The filtrate was concentrated togive the desired product as a viscous colorless oil (13.19 g, 91%). Theproduct was used in the subsequent reactions without furtherpurification.

¹H NMR (CDCl₃) δ 5.35 (m, 2H); 4.17 (t, 2H, J=6.70 Hz); 3.83 (s, 2H);2.1-1.9 (m, 4H); 1.75-1.55 (m, 2H); 1.45-1.2 (m, 22H); 0.95-0.85 (m,3H).

Example 12 Preparation of Oleyl Glycolyl 4-Methoxycinnamate

4-Methoxycinnamic acid (229 mg; 1.284 mmol; 1.0 equiv) was slurried in 1mL of toluene. Triethylamine (195 mg; 1.926 mmol; 1.5 equiv) was addedand the mixture was stirred at ambient temperature for 1 h to afford ahomogeneous solution. Oleyl bromoacetate (500 mg; 1.284 mmol) was added,and the mixture was stirred at ambient temperature for 3 h to indicate87% conversion of 4-methoxycinnamic acid to product after 3 h accordingto HPLC analysis. An additional two days of stirring afforded no furtherconversion. An additional 0.3 equiv of 4-methoxycinnamic acid was added,and the mixture was stirred overnight, then diluted with toluene, 3 MHCl (2 mL), and ethyl acetate. The bottom aqueous layer was removed, andthe top layer was washed with 5 mL of 5% sodium bicarbonate solution.The organic layer was dried and concentrated to afford oleyl glycolyl4-methoxycinnamate (0.51 g; 82%).

¹H NMR (CDCl₃) δ 7.73 (d, 1H, J=15.9 Hz); 7.50 (d, 2H, J=8.9 Hz); 6.91(d, 1H, J=8.9 Hz); 6.40 (d, 1H, J=15.9 Hz); 5.34 (m, 2H); 4.73 (s, 2H);4.18 (t, 2H, J=6.70 Hz); 3.84 (s, 3H); 2.1-1.9 (m, 4H); 1.75-1.55 (m,2H); 1.45-1.2 (m, 22H); 0.95-0.85 (m, 3H).

HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5μ thickness, 90:10methanol:water (containing 0.1% trifluoroacetic acid) for 20 min,detection at 325 nm): t_(R) 1.76 min (4-methoxycinnamic acid); t_(R)10.5 min (oleyl glycolyl 4-methoxycinnamate).

Example 13 Preparation of Oleyl Glycolyl Retinoate

Retinoic acid (203 mg; 0.674 mmol; 1.05 equiv) was slurried in 2 mL oftoluene. Triethylamine (78 mg; 0.77 mmol; 1.2 equiv) was added, and themixture was stirred at ambient temperature for 30 min to afford ahomogeneous solution. Oleyl bromoacetate (250 mg; 0.642 mmol) was addedand the mixture was stirred at ambient temperature overnight to indicate77% conversion of retinoic acid to product by HPLC analysis. Anadditional two days of stirring afforded no further conversion. Themixture was diluted with heptanes and washed with 3 M HCl (3 mL). Theorganic layer was washed with a 1:1 mixture of methanol:10% potassiumcarbonate (2×6 mL), then with 5% sodium bicarbonate solution (3 mL). Theorganic layer was dried and concentrated to afford oleyl glycolylretinoate (0.32 g; 82%).

¹H NMR (toluene-d₈) δ 6.85 (dd, 1H, J=15.0, 11.4 Hz); 6.30 (d, 1H,J=16.3 Hz); 6.20 (d, 1H, J=16.1 Hz); 6.04 (d, 1H, J=15.0 Hz); 6.02 (d,1H, J=11.5 Hz); 5.92 (s, 1H); 5.45 (m, 2H); 4.46 (s, 2H); 3.94 (t, 2H,J=6.7 Hz); 2.15-2.0 (m, 7H); 1.95 (t, 2H, J=6.3 Hz); 1.78 (s, 3H); 1.74(s, 3H); 1.65-1.1 (m, 34H); 1.08 (s, 6H); 0.95-0.85 (m, 6H).

HPLC (4.6×150 mm Zorbax SB-C8 column [Agilent], 3.5μ thickness, 90:10methanol:water (containing 0.1% trifluoroacetic acid) for 7 min,gradient to 95:5 methanol:water (containing 0.1% trifluoroacetic acid)over 1 min, hold for 18 min, gradient to 100% methanol over 1 min, holdfor 14 min, detection at 350 nm): t_(R) 3.8 min (retinoic acid); t_(R)23.6 min (oleyl glycolyl retinoate).

Example 14 Enzymatic Hydrolysis of Oleyl Glycolyl Retinoate

Oleyl glycolyl retinoate (50 mg; 0.082 mmol) was dissolved in 1 mL oftoluene. pH 7 Phosphate buffer (1 mL) was added followed by Novozym 435(50 mg). The mixture was stirred for 1 h at ambient temperature toafford 5% hydrolysis according to HPLC analysis. A control reactionwithout enzyme showed no hydrolysis.

Example 14 Enzymatic Hydrolysis of Retinyl O-Nicotinoylglycolate

Retinyl O-nicotinoylglycolate (50 mg) was dissolved in toluene (1 mL).An aqueous buffer (pH=7.0, 1 mL) was added, followed by Novozym 435 (25mg). The mixture was stirred at room temperature. At certain reactiontimes, the stirrer was stopped, and the mixture was allowed to settle.An aliquot of the top organic layer was taken and analyzed with HPLC todetermine the extent of hydrolysis, which was calculated according tothe following formula:

Hydrolysis (%)=100×LC Area_(retinol)/(LC Area_(retinol)+LCArea_(retinyl O-nicotinoylglycolate))

FIG. 1 shows the extent of hydrolysis over reaction time.

1. An ester of O-substituted hydroxy carboxylic acids having Formula 1, or 2:

wherein R and R¹ are independently selected from the group consisting of substituted and unsubstituted, branched- and straight-chain, saturated, unsaturated, and polyunsaturated C₁-C₂₂ alkyl, substituted and unsubstituted C₃-C₈ cycloalkyl, substituted and unsubstituted C₆-C₂₀ carbocyclic aryl, and substituted and unsubstituted C₄-C₂₀ heterocyclic; wherein the heteroatoms are selected from the group consisting of sulfur, nitrogen, and oxygen; with the proviso that said heterocyclic groups exclude ascorbic acid; and wherein n is 1-6.
 2. The ester according to claim 1 wherein R and R¹ are independently selected from the group consisting of substituted and unsubstituted, branched- and straight-chain saturated C₁-C₂₂ alkyl, substituted and unsubstituted, branched- and straight-chain C₂-C₂₂ alkenyl, substituted and unsubstituted, branched- and straight-chain C₄-C₂₂ dienyl, substituted and unsubstituted, branched- and straight-chain C₆-C₂₂ trienyl, substituted and unsubstituted, branched- and straight-chain C₈-C₂₂ tetraenyl, substituted and unsubstituted, branched- and straight-chain C₁₀-C₂₂ pentaenyl, substituted and unsubstituted C₃-C₈ cycloalkyl, substituted and unsubstituted C₆-C₂₀ carbocyclic aryl, substituted and unsubstituted C₄-C₂₀ heterocyclic, and mixtures thereof.
 3. The ester according to claim 1 wherein R is retinyl and R¹ is independently selected from the group consisting of substituted and unsubstituted, branched- and straight-chain saturated C₁-C₂₂ alkyl, substituted and unsubstituted, branched- and straight-chain C₂-C₂₂ alkenyl, substituted and unsubstituted, branched- and straight-chain C₄-C₂₂ dienyl, substituted and unsubstituted, branched- and straight-chain C₆-C₂₂ trienyl, substituted and unsubstituted, branched- and straight-chain C₈-C₂₂ tetraenyl, substituted and unsubstituted, branched- and straight-chain C₁₀-C₂₂ pentaenyl, substituted and unsubstituted C₃-C₈ cycloalkyl, substituted and unsubstituted C₆-C₂₀ carbocyclic aryl, substituted and unsubstituted C₄-C₂₀ heterocyclic, and mixtures thereof.
 4. The ester according to claim 2 or 3 wherein said alkyl, alkenyl, dienyl, trienyl, tetraenyl, pentaenyl, and cycloalkyl groups are substituted with at least one selected from the group consisting of C₁-C₆-alkoxy, carboxyl, amino, C₁-C₁₅ aminocarbonyl, C₁-C₁₅ amido, cyano, C₂-C₆-alkoxycarbonyl, C₂-C₆-alkanoyloxy, hydroxy, aryl, heteroaryl, thiol, thioether, C₂-C₁₀ dialkylamino, C₃-C₁₅ trialkylammonium and halogen.
 5. The ester according to claim 2 or 3 wherein said aryl group is at least one selected from the group consisting of phenyl, naphthyl, anthracenyl, and phenyl, naphthyl, or anthracenyl substituted with one to five substituents.
 6. The ester according to claim 5 wherein said one or five substituents of phenyl, naphthyl, or anthracenyl are selected from the group consisting of C₁-C₆-alkyl, substituted C₁-C₆-alkyl, C₆-C₁₀ aryl, substituted C₆-C₁₀ aryl, C₁-C₆-alkoxy, halogen, carboxy, cyano, C₁-C₆-alkanoyloxy, C₁-C₆-alkylthio, C₁-C₆-alkylsulfonyl, trifluoromethyl, hydroxy, C₂-C₆-alkoxycarbonyl, C₂-C₆-alkanoylamino and —OR⁴, —S—R⁴, —SO₂—R⁴, —NHSO₂R⁴ and —NHCO₂R⁴, wherein R⁴ is phenyl, naphthyl, or phenyl or naphthyl substituted with one to three groups selected from the group consisting of C₁-C₆-alkyl, C₆-C₁₀ aryl, C₁-C₆-alkoxy and halogen.
 7. The ester according to claim 2 or 3 wherein said heterocyclic group is selected from the group consisting of a 5- or 6-membered ring containing one to three heteroatoms selected from the group consisting of oxygen, sulfur and nitrogen.
 8. The ester according to claim 7 wherein said heterocyclic group is at least one selected from the group consisting of pyranyl, oxopyranyl, dihydropyranyl, oxodihydropyranyl, tetrahydropyranyl, thienyl, furyl, pyrrolyl, imidazolyl, pyrazolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, triazolyl, thiadiazolyl, oxadiazolyl, tetrazolyl, pyridyl, pyrimidyl, benzoxazolyl, benzothiazolyl, benzimidazolyl, and indolyl.
 9. The ester according to claim 7 wherein said heterocyclic group is substituted.
 10. The ester according to claim 9 wherein said heterocyclic group is substituted with at least one compound selected from the group consisting of C₁-C₆-alkyl, C₁-C₆-alkoxy, substituted C₁-C₆-alkyl, halogen, C₁-C₆-alkylthio, aryl, arylthio, aryloxy, C₂-C₆-alkoxycarbonyl, and C₂-C₆-alkanoylamino.
 11. The ester according to claim 9 wherein said heterocyclic group is substituted with a fused ring system.
 12. The ester according to claim 1 wherein said ester is represented by Formula 1; wherein n is 1; R—O is retinyl or oleyl; and R¹CO is selected from the group consisting of shikimoyl, 4-methoxycinnamoyl, feruloyl, salicyloyl, nicotinoyl, retinoyl and 2-cyano-3,3-diphenylacryloyl, or wherein said ester is represented by Formula 2 wherein n is 1, R—O is retinyl, and R¹ is 2-hydroxymethyl-4H-pyran-4-on-5-yl.
 13. A process to produce at least one ester of O-substituted hydroxy carboxylic acids having Formula 1, or 2:

wherein R and R¹ are independently selected from the group consisting of substituted and unsubstituted, branched- and straight-chain, saturated, unsaturated, and polyunsaturated C₁-C₂₂ alkyl, substituted and unsubstituted C₃-C₈ cycloalkyl, substituted and unsubstituted C₆-C₂₀ carbocyclic aryl, and substituted and unsubstituted C₄-C₂₀ heterocyclic; wherein the heteroatoms are selected from the group consisting of sulfur, nitrogen, and oxygen; and wherein n is 1-6, the process comprising: a) contacting an alcohol having Formula 3 R—OH  3 with a terminal halogen-substituted straight-chain carboxylic acid having Formula 4

or a short-chain ester having Formula 5 X(CH₂)_(n)COOR⁵  5 in the presence of an enzyme to produce an intermediate having the Formula 6,

wherein R is independently selected from the group consisting of substituted and unsubstituted, branched- and straight-chain, saturated, unsaturated, and polyunsaturated C₁-C₂₂ alkyl, substituted and unsubstituted C₃-C₈ cycloalkyl, substituted and unsubstituted C₆-C₂₀ carbocyclic aryl, and substituted and unsubstituted C₄-C₂₀ heterocyclic; wherein the heteroatoms are selected from the group consisting of sulfur, nitrogen, and oxygen; wherein R⁵ is a straight or branched C₁-C₄-alkyl or alkenyl, X is a halogen atom; and n is 1-6; and b) reacting said intermediate with a carboxylic acid or alcohol optionally in the presence of a base and optionally in the presence of a catalyst to produce said esters of Formula 1 or Formula 2, or both Formulas 1 and
 2. 14. The process according to claim 13 wherein Step a) is carried out in no solvent or an inert solvent; wherein said inert solvent is at least one selected from the group consisting of a cyclic ether solvent and an acyclic ether solvent, aromatic hydrocarbons, aliphatic or alicyclic saturated or unsaturated hydrocarbons, halogenated hydrocarbons, and polar aprotic solvents.
 15. The process according to claim 14 wherein said inert solvent is selected from the group consisting of toluene, heptanes, acetonitrile, and limonene.
 16. The process according to claim 13 wherein the temperature in Step a), in Step b) or in both Steps a) and B) is in a range of about −100° C. to about 100° C.
 17. The process according to claim 13 wherein the amount of said halogen-substituted acid or said short-chain ester is between about 0.85 and about 20 equivalents based on the weight of said compound in Formula
 3. 18. The process according to claim 13 wherein said enzyme is selected from the group consisting of protease, a lipase, and an esterase.
 19. The process according to claim 18 wherein said lipase is selected from the group consisting of Lipase PS (from Pseudomonas sp), Lipase PS-C (from Psuedomonas sp immobilized on ceramic), Lipase PS-D (from Pseudomonas sp immobilized on diatomaceous earth), Lipoprime 50T, Lipozyme TL IM, and Novozym 435 (Candida antarctica lipase B immobilized on acrylic resin).
 20. The process according to claim 13 further comprising removing water or alcohol byproducts, from said process in Step a).
 21. The process according to claim 13 wherein Step b) is carried out in no solvent or an inert solvent; wherein said inert solvent is at least one selected from the group consisting of water, a cyclic ether solvent, an acyclic ether solvent, an aromatic hydrocarbon, an aliphatic or alicyclic saturated or unsaturated hydrocarbon, a halogenated hydrocarbon, an ester, and a polar aprotic solvent.
 22. The process according to claim 21 wherein said inert solvent is selected from the group consisting of tetrahydrofuran, dimethyl formamide, dimethyl sulfoxide, acetone, acetonitrile, toluene, ethyl acetate, and water.
 23. The process according to claim 13 wherein said catalyst is selected from the group consisting of quaternary ammonium salts, quaternary phosphonium salts, and crown ethers.
 24. A cosmetic composition comprising the ester of claim
 1. 